Thermal ink jet printers have become nearly ubiquitous. These printers typically use semiconductor-based print heads that have individually-controlled printing elements that eject water-based inks onto a print media through microscopic holes under the control of a computer. Most so-called thermal ink jet (TIJ) printers use print heads that traverse a print media as ink is ejected, painting an image or text onto a page by the successive passes that the print head makes over the page.
The water-based ink that is used in most thermal ink jet printers is vaporized by heat produced by thin film resistors in the ink jet print head. While thermal ink jet printers are capable of providing consistently high quality printed output at relatively modest prices, they are not without operationally-induced short-comings. Heat and chemicals in the ink can react with metal components of the print heads.
Most thermal ink jet printers use print heads that have several individually-fired ink energizing elements. Each of the ink energizing elements causes small droplets of ink to be ejected from the print head onto a print media. When an ink energizing element fails, it can produce noticeable streaks or other anomalies in the printed output. When printing an image using a printer having an ink jet print head that traverses a page, a printing element failure is typically manifested by streaks or bands wherein color is missing.
Individual printing element failure can be caused by a variety of factors including corrosion, dried ink, or ink flow obstruction caused by particles or other impurities in the ink. When one-or more print elements fail, output print quality suffers. Discarding and replacing an ink jet printer print cartridge because individual printing elements have failed might be unnecessary if it were possible for the working print elements to compensate for the failed element. Similarly, when an ink jet printer is run in a xe2x80x9cdraftxe2x80x9d or single-pass mode wherein the print head passes over a selected area of the print medium being printed only once, printing quality also suffers. A method and apparatus that can compensate for a failed print element in an ink jet printer print head, i.e. continue to produce acceptable-quality print output even if a print element has failed, might produce considerable savings to ink jet printer users. A method of printing with larger and/or more numerous drops might improve print quality on a printing element failure as well as improve print quality when the printer is run in so-called draft mode.
In a thermal ink jet print head that uses an array (or arrays) of individually-addressable printing elements, printed output defects or anomalies that are caused by a printing element failure can be compensated for using the printing elements that are closest to the failed element. By increasing the quantity or volume of ink that is output from printing elements that are adjacent to a failed printing element, defects in a printed image or text can be effectively hidden or masked. Increasing ink output from the printing elements that are operational, so that the ink can bleed over or migrate into the area that would normally be painted by the failed element, streaking or banding in a printed output image or text can be reduced or even eliminated.